So – Dinosaur footprints!
One of the best places for dinosaur footprints in the country is the Isle of Wight. As well as there being several different types of dinosaur represented in the footprints on the island, there are also the two different types of footprint – moulds and casts.
If you remember from our series on ‘Types of Fossils’, a mould is where an animal has been – leaving an impression in the rock, and a cast is where that impression has been filled in by a different type of rock. Dinosaur footprints are found as both these types of fossils. But dinosaur footprints are also another type of fossil as well – a trace fossil. A trace fossil is when there is not an actual part of the animal preserved, but something it left behind – evidence of its existence. It could be feathers, trails, burrows, dung, and, of course, footprints!
Footprints are excellent, because they teach us so much about the animal, we can work out how big they were, how they walked, and sometime, when the skin impressions are left in the ground, ideas on what they looked like. But how did they form?
First, the ground must be wet. Just like when you walk down a muddy track, or a sandy beach, you leave the best footprints when it is wet and soggy. Once the dinosaur has left it’s prints, they then have to get preserved. Now, two rules:
One, the prints must be preserved quickly. If not, rain, the tides, and general wear and tear will destroy them very quickly. Just like your footprints on the beach when the tide comes in! Two: the footprints must be made in newly-forming rock – or they won’t get preserved! The sediment must be able to harden into rock, there has to be a sort of ‘glue’ to hold it all together. If it was just sand or mud, it wouldn’t work. You need the correct process to be able to preserve them, and it has to be done quickly!
We will now spend a bit of time exploring the Isle of Wight – some incredible finds are to be made there!